Jablite

[jpadie]

Hi all

 

Can I lay jablite directly over floor joists, then top with chipboard before the finish?  If so what is the maximum span for 50mm panels please?

 

Thanks

Justin

 

[MikeSharp01]

6 minutes ago, jpadie said:

Can I lay jablite directly over floor joists

Does not sound like a good plan as the floor will sink because the standard jablite EPS will compress at the joists. If you board it first then jablite it you stand a chance but I would check the compressive strength / square area value even then.

[Dave Jones]

2 hours ago, jpadie said:

Hi all

 

Can I lay jablite directly over floor joists, then top with chipboard before the finish?  If so what is the maximum span for 50mm panels please?

 

Thanks

Justin

 

no of course not. 50mm of eps is virtually pointless anyway

[Jenki]

No, for the reasons above.

If you post more details of what your trying to achieve you may get some help.  Is it ground floor/ first floor etc.

If your trying to improve insulation on the ground floor and you have suspended timber joists, option might be to remove the joists and create a floating floor on top of EPS insulation. Not straightforward but would produce fantastic thermal results.

[jpadie]

All good points thanks.

 

This is for a garden room conversion.  Small surface area of 12sqm. The base construction is joists over a void to earth.  Supported on a ring of bricks.

 

There's not much headroom (1m80 from the joists) so I'm trying to work out what the minimum practical layering over the joists would be.  There are current 10mm floor boards resting on 35x35 battens over the joists. 

 

There is no DPM at present.  

 

What's the optimum here, taking into account that this will never be the Ritz?  Leave the boards in place, dpm on top, jablite/something then chipboard then floor finishing?

[saveasteading]

Don't leave timber in a damp underfloor space then seal off the room above. It will rot.

Garden room conversion to what?

[jpadie]

2 hours ago, saveasteading said:

Don't leave timber in a damp underfloor space then seal off the room above. It will rot.

Garden room conversion to what?

 

Work shed to an office. 

 

Void above the dirt is not damp.  Plenty of air flow.  Timber joists sit a few inches above the earth.   Unfortunately where they end they sit on bricks and have perished. I am replacing them and will hang them on joist hangers going forward. 

[saveasteading]

3 hours ago, jpadie said:

Void above the dirt is not damp

But will be if you seal above the floor.

 

I would heat using an ashp or infrared, not insulate or seal the floor, and instead  use bubble wrap on walls and ceiling

 

It's a shed, partly  rotting already, and may never make a suitable office.

[jpadie]

5 hours ago, saveasteading said:

But will be if you seal above the floor.

 

I would heat using an ashp or infrared, not insulate or seal the floor, and instead  use bubble wrap on walls and ceiling

 

It's a shed, partly  rotting already, and may never make a suitable office.

 

 

It will have an ashp.   There will not be a concrete slab wherever I restore or rebuild (I am certainly rebuilding one side frame).

 

Does this mean that the floor cannot be practically insulated?

[saveasteading]

28 minutes ago, jpadie said:

Does this mean that the floor cannot be practically insulated?

That is my opinion. How about a concrete slab, poured from within? its not the best idea but a possibility.

[Dave Jones]

id  go for a sheet of ply/osb 12mm on the bottom for bearing, paint the underside of it with blackjack to waterproof it. polyethene brought up 200mm up the walls, 50mm celotex then a thinner sheet of ply/osb to use as a floor 9mm to make a nice celotex sandwich. 

 

The blackjack will help the rot from underneath and the expense of using marine ply.

 

50mm celotex while not good for a house will be massive in a shed, use the same in the walls/ceiling and make a box. tape all the joints will be cosy.

Edited July 29, 2023 by Dave Jones

[jpadie]

On 29/07/2023 at 07:19, Dave Jones said:

id  go for a sheet of ply/osb 12mm on the bottom for bearing, paint the underside of it with blackjack to waterproof it. polyethene brought up 200mm up the walls, 50mm celotex then a thinner sheet of ply/osb to use as a floor 9mm to make a nice celotex sandwich. 

 

The blackjack will help the rot from underneath and the expense of using marine ply.

 

50mm celotex while not good for a house will be massive in a shed, use the same in the walls/ceiling and make a box. tape all the joints will be cosy.

Thanks @Dave Jones  and apologies for delay in replying.  Am 500km away from home helping my youngest daughter move after completing uni.  

 

There are currently 10mm floor boards down on 35mm battens going to the floor joists.   A few of the floor boards (4) have the last 50mm with dry rot where they were touching some other joists that had rotted over 50 years.     The rest are good.  I'd intend to replace the perished boards.  In your schema would these serve instead of the 12mm osb?  I don't think I can get to the old boards easily to coat the underside without ripping them up... But as said, after 50 years they are still ok except for a small area of a small number.   Taking the boards up is an issue as the ends rest under the wall frames and I'm not keen on fully dismantling the shed unless all other routes are barred!  It's sturdy and rot free apart from one area of issue, and still largely true to square.  

[Dave Jones]

will be fine, just put polythene down over them to stop any damp coming up and crack on.